Avoid draining the ArrayPool with undisposed JsonDocuments

src/Microsoft.IdentityModel.JsonWebTokens/Json/JsonClaimSet.cs

@@ -22,17 +22,20 @@ internal class JsonClaimSet
 
         internal JsonClaimSet(JsonDocument jsonDocument)
         {
-            RootElement = jsonDocument.RootElement;
+            // This method is assuming ownership of the JsonDocument, which is backed by one or more ArrayPool arrays.
+            // We need to dispose of it to avoid leaking arrays from the pool.  To achieve that, we clone the root element,
+            // which will result in a new JsonElement being created that's not tied to the original and that's not backed by
+            // ArrayPool memory, after which point we can dispose of the original to return the array(s) to the pool.
+            RootElement = jsonDocument.RootElement.Clone();
+            jsonDocument.Dispose();
         }
 
-        internal JsonClaimSet(byte[] jsonBytes)
+        internal JsonClaimSet(byte[] jsonBytes) : this(JsonDocument.Parse(jsonBytes))
         {
-            RootElement = JsonDocument.Parse(jsonBytes).RootElement;
         }
 
-        internal JsonClaimSet(string json)
+        internal JsonClaimSet(string json) : this(JsonDocument.Parse(json))
         {
-            RootElement = JsonDocument.Parse(json).RootElement;
         }
 
         internal JsonElement RootElement { get; }